Mobile phones, personal digital assistants (PDAs), digital cameras, MP3 players, and other portable electronic devices utilize SSL devices (e.g., white light LEDs) for background illumination. However, true white light LEDs are not available because LEDs typically only emit light at one particular wavelength. For human eyes to perceive the color white, a mixture of wavelengths is needed.
One conventional technique for emulating white light with LEDs includes depositing a converter material (e.g., a phosphor) on a light emitting material. For example, as shown in FIG. 1A, a conventional LED device 10 includes a support 2 carrying an LED die 4 and a converter material 6 deposited on the LED die 4. The LED die 4 can include one or more light emitting components. For example, as shown in FIG. 1B, the LED die 4 can include a silicon substrate 12, N-type gallium nitride (GaN) material 14, an indium gallium nitride (InGaN) material 16 (and/or GaN multiple quantum wells), and a P-type GaN material 18 on one another in series. The LED die 4 can also include a first contact 20 on the P-type GaN material 18 and a second contact 22 on the N-type GaN material 14. Referring to both FIGS. 1A and 1B, in operation, the InGaN material 16 of the LED die 4 emits a blue light that stimulates the converter material 6 to emit a light (e.g., a yellow light) at a desired frequency. The combination of the blue and yellow emissions appears white to human eyes if matched appropriately.
One operational difficulty of the LED device 10 is that the LED die 4 produces a significant amount of heat. The generated heat raises the temperature of the converter material 6, and thus causes the converter material 6 to emit light at a different frequency than the desired frequency (a phenomenon commonly referred to as “thermal quenching”). As a result, the combined emissions would appear off-white and may reduce the color fidelity of electronic devices. Accordingly, several improvements in managing the thermal load in LED packages may be desirable.